Metal Structures Having Weld Zone Improved Fracture Toughness And Method for Manufacturing the Same

摘要

The present invention relates to a metal structure and a manufacturing method thereof which artificially form a notch and a fine crack on a base metal portion on a position separated from a welded portion whose mechanical property is weak to transfer a fracture start portion from the welded portion to the base metal portion and increase crack propagation energy on the base metal portion to improve fracture toughness of the entire structure. According to the present invention, the metal structure has a base metal portion and a welded portion. Impact absorption energy (B) of the base metal portion is defined to be the sum of crack start energy (B_i) and crack propagation energy (B_p). Fracture impact aboption energy (W) of the welded portion is defined to be the sum of crack start energy (W_i) and crack propagation energy (W_p). A notch is dented on a surface of the base metal portion on a position separated from the welded portion in a prescribed depth to allow the crack start energy (B_i) of the base metal portion to become smaller than the crack start energy (W_i) of the welded portion. A plurality of fine cracks are dented on the notch while crossing perpendicularly to a longitudinal direction of the notch to allow a difference (W_p-B_p) of the crack propagation energy between the welded portion and the base metal portion to become larger than a difference (W_i-B_i) of the crack start energy between the welded portion and the base metal portion.